Method for the manufacture of regenerated cellulose materials



Sept. 12, 1950 M. D. RODGERS 2,521,743

ms'ruon FOR THE MANUFACTURE OF REGENERATED CELLULOSE MATERIALS Filed Dec. 26, 1947 MARCUS 0. RODGERS 44 INVENTOR A T TORNE Y Patented Sept. 12, 1950 carnal) STATES PATENT OFFICE METHOD FOR THE MANUFACTURE OF REGENERATED CELLULOSE MATERIALS Marcus D. Rodgers, Lakewood, Ohio, assignor to Industrial Rayon Corporation, Cleveland, Ohio, a corporation of Delaware Application December 26, 1947, Serial No. 794,035

29 Claims. (01. 18-54) A suitable viscose spinning solution is extruded into an acid coagulating bath usually containing sulfuric acid and sodium sulfate. Such baths may also contain minor amounts of other materials such as, for example, zinc sulfate which influence the rate of regeneration of the filaments. Before the regeneration of the resulting yarn is complete the yarn is usually stretched in varying amounts depending on the ultimate use intended for the yarn. The yarn at this stage usually contains unregenerated cellulose xanthate together with a number of undesirable by-products such as sodium sulfate, carbon disulflde, hydrogen sulfide, free sulfur, and combined sulfur such as the sulfides and the thiocarbonates of lead, zinc, iron, etc.

In processing and finishing freshly extruded yarn a number of separate treatments are generally required as hereinafter set forth. This is generally true whether a pot, spool or continuous processing method is employed. The processing steps referred to are usually in the following order; (1) prolonged exposure to acidsolution to completely decompose the xanthates and metal thiocarbonates remaining in the yarn; (2) washing the yarn to remove adhering acid liquid; (3) treatment with a desulfurizing solution such as an alkaline sodium sulfide solution to remove sulfur present in the yarn in the free and combined state; (4) washing with water to remove the adhering desulfurizing solution and by-products; (5) treatment with a bleaching solution; (6)

washing with an aqueous solution to remove the adhering bleach solution; and (7) finally drying the finished yarn.

The present invention provides a new and considerably shortened process for the production of rayon yarn having physical properties and uniformity of physical and dyeing properties equal to or better than commercially acceptable standards. The invention further provides a method whereby the cost of processing freshly extruded yarn is materially reduced as regards machinery, chemicals and man-hours employed per pound of yarn produced. By the present process a considerable reduction in the processing time between the extrusion stage and the final washing stage of a thread is effected generally by reducing the number of separate processing stages and by combining the action of several stages.

In accordance with the process of the invention a viscose spinning solution is extruded into an acid coagulating bath and the resulting material is withdrawn from the bath and then treated with an aqueous acid solution. The aqueous acid treatment is performed at a temperature between about 65 and 100 C. The material is then treated with an aqueous oxidizing solution and thereafter the oxidizing solution is removed from the treated material.

In practicing the present invention the viscose spinning solution may be prepared from cotton linters or from refined wood pulp that is substantially free from lignin. Such refined wood pulps for use in rayon manufacture usually contain more than about 90% alpha cellulose and are substantially free from lignin, the concentration of the latter material being usually less than 0.5%. Refined wood pulps containing less than about 0.2% lignin may be used with particular advantage.

The resulting viscose solution may be extruded into the customary type acid coagulating bath; such baths usually contain sulfuric acid in a concentration, by weight, of about 7% to 13% in association with approximately 13% to 25% sodium sulfate. Sometimes such baths also contain other salts such as, for example, zinc sulfate in concentrations of the order of 1 to 5%. Minor amounts of organic compounds such as glucose or various surface-active materials may also be present in the coagulating bath.

The aqueous acid solution employed in treating the yarn after it has been formed in the coagulating bath should contain sufllcient acid to further the regeneration of the yarn. The aqueous acid solution may advantageously have substantially the same composition as the coagulating bath, or if desired a coagulating bath composition which has been suitably diluted with water may be employed. Alternatively the aqueous acid solution may contain merely an acid such as sulfuric acid in a concentration equal to or less than that present in the coagulating bath. It is desirable to maintain the concentration of acid in the aqueous acid solution in the range of about 1 to 5% by weight.

It has been found especially advantageous to employ aqueous acid solutions in which the ratio, by weight, or dissolved salts to acid is less than that in the acid coagulating bath solution employed. Such d'nsolved salts may, for example,

'be sodium sulfate, zinc sulfate, etc, depen on the type of coagulating bath employed.

The treatment with the aqueous acid solution is advantageously performed at temperatures between about 65 C. and 100 C. In general the higher temperatures are most effective in reducing the treatment time, and from this standpoint temperatures in the range of about 75 to about 85 C. or somewhat higher are especially advantageous.

The treatment of freshly extruded yarn with the aqueous acid solution may b carried to the stage where the yarn is substantially completely regenerated or if desired the regeneration of the yarn may b carried forward to a lesser degree. Manifestly, however, the extent of the regeneration accomplished during the treatment with the aqueous acid solution must be correlated with the subsequent treatment with the aqueous oxidizing solution as contemplated by the process of this invention in order to achieve maximum economy and efficiency.

The subsequent chemical treatment of the yarn in accordance with this process involves the treatment with an aqueous oxidizing solution. It is believed that such treatment completes the regeneration of or destroys any dimcultly convertible xanthate residues which may remain in the yarn after the aqueous acid treatment or any other objectionable impurities such as for example, metal thiocarbonates which may be present in the yarn.

The aqueous oxidizing solution that may be employed in accordance with the present invention may contain any of the common oxidizing agents that are used for the oxidation of cellulosic materials, provided however, that they are employed under conditions of concentration, temperature, pH, time of treatment, etc. that will not chemically degrade regenerated cellulose materials such as, for example, the viscose rayon yarn of the present invention.

In general for the purpose of the present process relativelymild aqueous oxidizing conditions are advantageously employed. Particularly advantageous are those conditions that are not as strong as the conditions ordinarily employed for th bleaching of cotton.

Among the oxidizing agents that may be used to make up the aqueous oxidizing solution of the present process may be mentioned generally certain oxy-halogen compounds, such as the hypohalites and halites; and the soluble salts of the per compounds, such as the peroxides, permanganates, perborates, persilicates, percarbonates, persulfates, etc.

Among the hypohalites may be mentioned the hypohalous acids, such as hypochlorous, hypobromous and the hypoiodous acids together with compounds that form such hypohalous acids in aqueous solutions such as, for example, the soluble alkali metal and alkaline-earth metal salts of such hypohalous acids. Typical of such alkali metal hypohalite salts are the sodium and potassium hypochlorites and the corresponding hypobromites. A typical example of the alkaline-earth metal hypohalite salts is the chloride of lime, calcium hypochlorite.

As examples of the halites may be mentioned the chlorous, bromous and iodous acids together with the soluble alkali metal and alkaline-earth metal salts thereof. Typical of the metal salts of such acids are the chlorites, bromites and iodites of sodium, potassium or calcium.

Among the peroxides may be mentioned hydrogen peroxide and the hydrogen peroxide liberat ing compounds such as the alkali and alkalineearth metal peroxides. A typical example of such metal peroxides is sodium peroxide.

As examples of the other per compounds may be mentioned ammonium or sodium persulfate and the alkali metal permanganates.

In the practice of the present invention there is no intervention of a desulfurizing treatment on the yarn between the aqueous acid treatment and the oxidation treatment of the process.

After the yarn has been subjected to the aqueous oxidizing solution treatment the oxidizing solution adhering to the treated yarn may be removed by any known means. Advantageously aqueous solutions may be employed very effectively to wash oil the oxidizing solution together with impurities formed during the oxidation treatment. For example, a wash with water between the temperatures of about 30 and C. may b employed very effectively.

In practicing the present invention the freshly extruded yarn withdrawn from the acid coagulating bath may, if desired, be stretched by any known method both before or during the treatment with the hot aqueous acid solution of the process. Particularly advantageous results may be derived by stretching between about 10% and 50% before the aqueous acid treatment.

Further, the process of the present invention may be practiced by employing the continuous methods of processing yarn such as, for example, the methods employing devices and apparatuses wherein the yarn undergoing treatment is advanced and stored in a plurality of generally helical turns. One such method of processing involves the use of a series of thread-advancing, thread-storage reels such as those described in the Knebusch Patent 2,210,914.

For the purposes of illustration the invention will be described in connection with the accompanying drawings in which:

Figure 1 illustrates a series of thread-advancing, thread-storage reels on which freshly extruded viscose yarn may be processed;

Figure 2 illustrates a thread-advancing, thread-storage reel having a plurality of liquid treatment zones capable of processing viscose yarn in accordance with the present invention.

For convenience the invention will be further described in the following examples where reference will be made to the 'above identified drawings, it being understood that the invention is not intended to be limited to the specific details set forth in the examples.

Example 1 A denier, 40 filament viscose rayon yarn having very desirable and uniform properties may be produced as follows: A viscose spinning solution containing about 6.5% sodium hydroxide and about 8% cellulose is prepared in the conventional manner from a refined wood pulp containing approximately, by weight, 92% alpha cellulose, 2% beta cellulose, 5% gamma cellulose, and less than about 0.2% lignin. After being ripened to an index of approximately 4 (sodium chloride) the viscose is extruded through a suitable spinneret ll positioned in a coagulating bath I2 contained in trough II, the bath l2 being maintained at approximately 45 C. and containing approximately, by weight, 12% sulfuric acid, 22% sodium sulfate, 1.5% zinc sulfate and 0.1% of a cation-active agent. The spinning solution is extruded at the rate of about 14 grams er minute and the formed yarn ll, after travelling through about inches of the bath liquid, is collected at the rate of about 62.5 meters per minute on a first thread-storage, thread advancing reel I 5 having a diameter of about 5% inches. The freshly extruded yarn I I, while wet with acid bath liquid, is stored on the reel l5 for about seconds in the form of a helix. This is accomplished by maintaining about 40 helical turns of thread in the helix and rotating the reel [5 at the rate of about 136 R. P. M.

Thereafter the yarn I4 is discharged from .the reel I5 and it is conducted to a succeeding thread-advancing reel l8 of about the same diameter but operating at a peripheral speed of about 78 meters per minute or 170 R. P. M. As.

a result the yarn between the reel l5 and the next reel I8 is stretched about The yarn entering the reel I8 is advanced and stored thereon for about 50 seconds in the form of a helix having about 130 turns of yarn. About 400 cc. per minute of an aqueous acid solution 2| at an elevated temperature is applied to the helix on the reel 13 by means of a delivery tube 25 and the solution is applied at approximately the thread discharge end of the helix. The aqueous acid solution 2| contains about 2.5%, by weight, sulfuric acid and about 5%, by weight, sodium sulfate. The acid solution 2| is maintained at a temperature of about 70 C. while in contact with the yarn on the reel l8. A housing 3| encompasses the reel I 8 and assists in maintaining this temperature. The reel is mounted at a, slight angle so that the acid solution 2| applied at the thread discharge end thereof is caused to flow towards the thread take-up end of the reel to form a continuous layer or film blanket of the solution covering part or all of the helix. The acid solution 22 drops off the reel into trough 23 below the reel from which it is reclaimed for reuse.

The yarn H from the reel I8 is then conducted to a succeeding reel 25 having about the same diameter and travelling at about the same peripheral speed as the reel l8. The number of helical turns of yarn on the reel 25 is about 110, thereby storing the yarn thereon in the form of a helix for about 40 seconds. About 350 cc. per minute of a dilute aqueous sodium hypochlorite solution 28, maintained at a temperature of about 50 0., is applied by a delivery tube 21 at approximately the thread discharge end of the advancing helix. The solution is caused to flow as a continuous layer or film blanket to the thread take-up end of the helix. The hypochlorite solution has a pH between about 9 and 10, an available chlorine content of about 0.01% and between about 0.00% and 0.05%, by weight, sodium hydroxide. The hypochlorite solution 25 discharged from the reel 25 is subsequently collected by the trough and disposed of as a waste product.

The yarn H from the reel 25 is conducted to a succeeding reel 33 having about the same diameter and about the same speed of rotation as the preceding reels l8 and 25. The yarn on the reel 33 advances as a helix consisting of about 150 turns, thereby storing the yarn thereon for about 53 seconds. Soft water 35, delivered by a tube 35 and maintained at a temperature of about 90 C. is applied to the helix at the rate of about 400 cc. per minute. The water 35 is applied in tne same manner as the solutions applied to reels I5 and 25. The discharged water 31 from reel 33 is removed by a trough 38 and is reused to make up the hypochlorite solution The yarn H from reel 33 is conducted to a yarn drying reel 40 enclosed by a housing 4|. The dried yarn I5 is then discharged from the reel 40 and is thereafter conducted to a thread collecting device 43 and wound thereby as a package on a bobbin 44.

The yarn produced in accordance with this example is substantially free of objectionable impurities such as, for example, xanthate residues and metal thiocarbonates, i. e. it will not turn brown when boiled for 15 minutes with an aqueous 0.25% trisodium phosphate solution. The finished yarn contains between about 0.03% and 0.10%, by weight, sulfur in the free state. The yarn has very desirable strength and elongation properties and is completely uniform both in physical properties and in appearance. The knitted or woven fabric made therefrom may be dyed in any shade with complete uniformity. Since the minor amount of sulfur contained in the finished yarn is in a free state such sulfur may, ii. desired, be easily scoured off the yarn or fabric by washing with water at about C. for about 15 minutes. This operation usually takes place when a knitted or woven fabric is given its customary aqueous scouring treatment prior to dyeing.

Example 2 A 1100 denier 480 filament high tenacity viscose yarn is produced in the manner and under the conditions described in Example 1 except for the following:

The viscose spinning solution is made from a refined wood pulp containing approximately, by weight, 95% alpha cellulose, 1.5% beta cellulose, 2.5% gamma cellulose and about 0.08% lignin. The viscose is extruded through a 480 hole spinneret into a coagulating bath containing, by weight, about 9% sulfuric acid, 20% sodium sulfate, and 4.5% zinc sulfate. Thread-advancing, thread-storage reels having greater yarn storage capacities are employed. The yarn is stretched about 45% prior to the aqueous acid solution treatment and the latter treatment is performed at about C. Yarn produced in accordance with this example has a high tensile strength and desirably uniform physical properties. It is especially suited for the manufacture of reinforcing cords for reinforced rubber structures such as tires, belts, hose and the like.

Example 3 A 150 denier 40 filament viscose yarn is produced in the manner and under the conditions described in Example 1 except for the following:

The stretched yarn stored on reel I8 is treated with an aqueous acid solution containing about 4%, by weight, sufuric acid and less than 1% total dissolved salts. The temperature of such aqueous acid treatment is maintained at about C. The oxidizing treatment on reel 25 is performed by an aqueous sodium hypochlorite solution having a pH of about 6 and an available chlorine content of about 0.005%. The yarn on such reel 25 is stored for about 53 seconds by maintaining about helical turns of yarn thereon. The washed and dried yarn produced in this example is also characterized by its uniformity in appearance and physical properties.

Example 4 A 150 denier 40 filament viscose yarn is produced in a manner and under the conditions described in Example 1 except for the following:

An aqueous acid solution is employed containing about 2%, by weight, sulfuric acid and substantially no dissolved salts. The temperature of the aqueous acid treatment is maintained at about 90 C. A sodium chlorite oxidizing solution is employed at a. temperature of about 54 C. The chlorite solution has a pH between about 6 and 7, and an available chlorine content of about 0.06%.

Example A 150 denier 40 filament viscose yarn is produced in the manner and under the conditions described in Example 1 except for the following:

oxidizing solution that could besafely employed on such a yarn without tendering and degrading it. Advantageously the conditions of the aqueous The aqueous acid treatment, the oxidizing solution treatment and the water treatment are all performed on a single thread-advancing, threadstorage device having a plurality of separate treatment zones. Such devices are known to the art and are advantageously adaptable to the present process.

In describing the treatment performed on such a device reference will be made to Figure 2 of the drawings. The yarn processed in this example is the yarn l4 leaving the reel l5 as described in Example 1 and illustrated in Figure 1. This yarn is conducted to the supported end of an elongated multi-zone type, thread-advancing. thread-storage reel 49 of Figure 2 over which the yarn continues to travel in a series of helices formed by periodically lifting the yarn off the reel onto godet guides and returning it to the reel. The yarn advances as a helix over the reel and is first treated with a dilute aqueous acid solution 52 delivered by a tube 5|. solution 52 flows toward the supported end of the reel and is discharged into a compartmented trough 55 below the reel.

Thereafter the thread is passed over a resiliently mounted godet wheel 53 positioned below the thread-advancing reel and then advanced again as a, second helix on the reel where it is next treated with a dilute aqueous oxidizing solution 59 delivered by a tube 58. The oxidizing solution 59 flows towards the take-up end of the helix and drops off into its respective compartment of the trough 55. The yarn is then passed over a godet guide '51 then returned to the reel and advanced as a third helix. .The yarn in this helix is treated with water 61 delivered by a tube 66. The water drops oil the reel into its respective compartment of the trough 55. The washed yarn I4 is then again led off the reel over a godet guide 65 then back onto the reel and advanced as a fourth helix through a yarn-drying zone 13. The yarn is dried by warmed air supplied by a blower 12 positioned adjacent the reel. The dried yarn is subsequently discharged from the drying-zone l3 and is conducted to a yarn collecting device 15 where it is packaged to form a bobbin 16. The yarn produced in accordance with this example is similar in quality and uniformity to the yarn of Example 1.

As previously indicated the conditions of the oxidation treatment are controlled to a large extent by the degree of cellulose xanthate regeneration and destruction of impurities accomplished on the yarn by the hot aqueous acid treatment and also by the specific oxidation conditions such as treatment Lime, temperature, pH, and concentration of the particular oxidant in the aqueous The acid acid treatment may be such that the greater portion of the impurities in the yarn such as the undestroyed xanthates and thiocarbonates be destroyed and removed so that only a mild oxidation treatment is thereafter necessary and less free sulfur remains in the finished yarn after the oxidation treatment.

With any given oxidant each of the specific oxidation conditions above referred to may be varied as desired by making corresponding adjustments in one or more of the other conditions. The methods of adjusting such conditions for any given oxidizing solution so as to prevent oxidative degradation are well known in the bleaching art. It is well known, for example, that the rate of oxycellulose formation on any cellulosic material is considerably influenced by the pH of the oxidizing solution. The most rapid reaction for most oxidants occurs at'or near the neutral point. This may be one of the reasons why the bleaching art prefers to operate in definitely acid or alkaline conditions, within a certain narrow range. Further, in this connection it is well known that the oxidation of cellulose under strongly alkaline conditions readily degrades cellulose. It is known also that for any given concentration of an oxidant in an aqueous solution an increase in temperature greatly accelerates the oxidizing action and at the same time accelerates the degrading action of cellulose. In treating regenerated cellulose such as viscose yarn with aqueous oxidizing solutions special attentionis usually given to avoid degradation since there exists relatively less quantitles of non-cellulosic materials which may be selectively oxidized.

As illustrated by the examples, the process of the present invention is particularly suited for processing yarn continuously on one or more thread-advancing, thread-storage devices. For example, it is particularly adaptable to meet the limited treating-time requirements for each treatment stage in such methods of processing. Likewise it is particularly adaptable to meet the coordinated treating times required in such methods as between the various processing stages.

Hereinafter for the purposes of the present invention, yarn advanced and stored in the form of a plurality of generally helical turns, such as, for example, the form of a yarn stored on a pair of rollers or drums or on a unitary thread-advancing device or reel, will be referred to as an advancing helix.

In the processing of advancing helices of yarn by continuous processing methods, it has been found advantageous to store freshly extruded bath-wet, yarn in the form of a helix for a limited time prior to treatment with the hot aqueous acid solutions of the present process and particularly advantageously prior to stretching the yarn.

The aqueous treating solutions of the present invention may be applied to an advancing helix of yarn in a. number of known ways. The helix may be advanced through a trough containing the treating solution or the solution may be applied in the form of a stream or spray from the inside, outside, top, bottom or side of an advancing helix, depending on the type of thread-advancing, thread-storage device employed.

Mild aqueous hypochlorite solutions have been found particularly advantageous as oxidizing solutions for the continuous processing of yarn by the present process. Not only are the hypochlorites cheap chemical agents but they may be employed at extreme dilutions, thus rendering such solutions expendable after useage as waste products while at the same time being safe and sufliciently effective for the oxidation treatment of the present process. Although they may be employed safely and effectively both under limited acid or alkaline pH conditions, particular advantages are derived by employing pH conditions from about neutral to about 10. Similar advantages are derived with hypochlorite solutions having an available chlorine content between about 0.005% and 0.1%, and even better between about 0.005% and 0.05%.

Advantageously a. hypochlorite solution employed under the above conditions can be simultaneously utilized both as a washing agent for an acid-wetyarn about to undergo oxidation treatment, and also as an oxidizing agent. Typical specific conditions present when treating an acidwet yarn with a hypochlorite oxidizing solution may be illustrated, for example, by theoxidizing conditions employed in Example 1. A sodium hypochlorite solution was used having a pH between about 9 and and an available chlorine content of about 0.01%. After application thereof to the yarn helix on the reel such solution quickly assumes a pH of about 6.5 while the solution discharged from the reel has a pH of about 2, an available chlorine content of about 0.007% and from about 0.2% to 0.3%, by weight, sulfuric acid.

Similarly, sodium chlorite oxidizing solutions employed under mild conditions are especially suited for the continuous processing of yarn by the present process. Chlorite solutions having a pH between about 3 and 7 and an available chlorine content between about 0.01% and 1.0% may be employed with advantage. Even greater advantages are derived with chlorite solutions having a pH between about 6 and '7 and an available chlorine content between about 0.01% and 0.1%.

I claim:

1. A process for the manufacture of viscose yarns, strips, films and the like which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting material from said bath; treating said material at a temperature maintained between about 65 C. and 100 C. with an aqueous acid solution; treating said material with an aqueous oxidizing solution; and thereafter removing said oxidizing solution from said treated material; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

2. A process for the manufacture of viscose yarns, strips, films and the like which comprises extruding a viscose solution into an acid coagulatin bath; withdrawing the resulting material from said bath; treating said material at a temperature maintained between about 65 C. and 100 C. with an aqueous acid solution; treating said material with an aqueous oxdizing solution comprising a hypohalite; and thereafter removing said oxidizing solution from said treated 'material; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

3. A process for the manufacture of viscose yarns, strips, films and the like according to claim 2 in which the aqueous oxidizing solution comprises a halite.

4. A process for .the manufacture of viscose yarns, strips, films and the like according to claim 2 in which the aqueous oxidizing solution com- I prises a soluble per compound.

' yarns, strips, films and the like according to claim 2 in which the aqueous oxidizing solution comprises an alkali metal hypohalite.

7. A process for the manufacture of viscose yarns, strips, films and the like accordin to claim 2 in which the aqueous oxidizing solution com--' prises an alkali metal halite.

8. A process for the manufacture of viscose yarns, strips, films and the like according to claim 2 in which the aqueous oxidizing solution comprises sodium hypochlorite.

9. A process for the manufacture of viscose yarns, strips, films and the like which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting material from said bath; treating said material with an aqueous sulfuric acid solution having an acid concentration less than that of said acid coagulating bath, said aqueous acid treatment being performed at a temperature between about 65 C. and C.; treating said material with an aqueous oxidizin solution comprising a soluble hypochlorite; and thereafter removin said oxidizing solution from said treated material; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

10. A process for the manufacture of viscose rayon yarn according to claim 9 in which the aqueous oxidizing solution comprises an alkali metal chlorite.

11. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; treating said yarn with an aqueous sulfuric acid solution having an acid concentration between about 1% and 5%, by weight, said aqueous acid treatment bein performed at a temperature between about 65 C. and 100 C.; treating said yarn with an aqueous oxidizin solution comprising sodium hypochlorite; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

12. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; treatin said yarn at a temperature maintained between about 65 C. and 100 C. with an aqueous sulfuric acid solution having an acid concentration between about 1% and 5%, by weight;

treating said yarn with an aqueous oxidizing solution comprising sodium hypochlorite, said hypochlorite solution having a pH between about '7 and 10 and an available chlorine content between about 0.005% and 0.1%; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

13. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; treating said yarn at\a temperature maintained between about 65 C. and 100 C. with an aqueous sulfuric acid solution; treating said yarn with an aqueous oxidizing solution comprising sodium chlorite; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment -between it and said aqueous acid treatment.

14. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; treating said yarn with an aqueous sulfuric acid solution having an acid concentration between about 1% and 5%, by weight, said aqueous acid treatment being performed at a temperature between about 65 C. and 100 C.; treating said yarn with an aqueous oxidizing solution comprising sodium chlorite, said sodium chlorite solution having a-pH between about 3 and 7 and an available chlorine content between about 0.01% and 1.0%; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

15. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; treating said yarn at a temperature maintained between about 65 C. and 100 C. with an aqueous sulfuric acid solution; treating said yarn with an aqueous oxidizing solution comprising a hypohalous acid; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

16. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; continuously but temporarily advancing and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing a plurality of turns of said helix through an aqueous acid solution, said aqueous acid treatment being performed at a temperature between about 65 C. and 100 C.; continuously but temporarily advancing and storing said treated yarn in the form of a second helix; advancing a plurality of turns of said second helix of yarn through an aqueous oxidizing solution; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment bein performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

17. A process for the manufacture of viscose rayon yarn according to claim 16 in which the aqueous oxidizing solution comprises a hypohalite.

18. A process for the manufacture of viscose rayon yarn according to claim 16 in which the aqueous oxidizing solution comprises a halite.

19. A process for the manufacture of viscose rayon yarn according to claim 16 in which the aqueous oxidizing solution comprises an alkali metal hypohalite.

20. Aprocess .for the manufacture of viscose rayon yarn according to claim 16 in which the aqueous oxidizing solution comprises an alkali metal halite.

21. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; continuously but temporarily advancing and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing a plurality of turns of said helix through an aqueous sulfuric acid solution having an acid concentration less than that of said acid coagulating bath, said aqueous acid treatment being performed at a temperature between about 65 C. and C.; continuously but temporarily advancin and storing said treated yarn in the form of a second helix; advancing a plurality of turns of said said second helix of yarn through an aqueous oxidizing solution comprising a soluble hypochlorite; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

22. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; continuously but temporarily advancin and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing a. plurality of turns of said helix through an aqueous sulfuric acid solution having an acid concentration between about 1% and 5%, by weight, said aqueous acid treatment being performed at a temperature between about 65 C. and 100 0.; continuously but temporarily advancing and storing said treated yarn in the form of a second helix; advancing a plurality of turns of said second helix of yarn through an aqueous oxidizing solution comprising sodium hypochlorite, said hypochlorite solution having a pH between about 7 and 10 and an available chlorine content between about 0.005% and 0.1%; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

23. A process for the manufacture of viscose rayon yarn according to claim 22 in which the aqueous sulfuric acid solution has a dissolved salt to acid ratio less than that of the acid coagulating bath and the sodium hypochlorite solution has an available chlorine content between about 0.005% and 0.05%.

24. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yam from said bath; stretching said yarn between about 10% and 50% continuously but temporarily advancing and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing a plurality of turns of said helix through an aqueous acid solution, said aqueous acid treatment being performed at a temperature between about 65 C. and 100 C.; continuously but temporarily advancing and storing said treated yarn in the form of a second helix; advancing a plurality of turns of said second helix of yarn through an aqueous oxidizing solution comprising sodium hyl3 pochlorite, said hypochlorite solution having a pH between about 7 and 10 and an available chlorine content between about 0.005% and 0.1 and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

25. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resulting yarn from said bath; continuously but temporarily advancing and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing said helix through a plurality of aqueous solution treatment zones, at least one of said zones comprising a treatment with an aqueous acid solu tion, and at least one of the succeeding zones comprising a treatment with an aqueous oxidizing solution; said aqueous acid treatment being performed at a temperature between about 65 C. and 100 0.; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

26. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; with- 3 drawing the resulting yarn from said bath; continuously but temporarily advancing and storing said yarn in the form of a helix having a plurality of closely spaced turns; advancing said helix through a plurality of aqueous treatment zones; at least one of said zones comprising a treatment with an aqueous sulfuric acid solution having an acid concentration less than that of said acid coagulating bath; at least one of the succeeding zones comprising a treatment with an aqueous oxidizing solution comprising sodium hypochlorite; and at least one of the zones following said oxidizing treatment comprising a treatment with an aqueous solution for removing said oxidizing solution from said treated yarn; said aqueous sulfuric acid treatment being performed at a temperature between about 65 C. and 100 C.; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment. 27. A process for the manufacture of viscose rayon yarn which comprises extruding a viscose solution into an acid coagulating bath; withdrawing the resultingyarn from said bath; transferring said yarn, while wet with said acid bath 55 1,128,624

liquid, to a first thread-advancing, thread-storage reel on which said yarn is temporarily stored and advancedintheformofahelixhavingaplu- 14 rality of closely spaced turns, the number of turns being suiiicient to store the yarn thereon for a period of time between about 15 and 60 seconds; transferring the yarn discharged from said first reel, while wet with said acid bath liquid, to a second thread-advancing, thread-storage reel having a greater peripheral speed, thereby stretching said yarn between about 10% and the number of helical turns of yarn on said second reel being sufflcient to temporarily store said stretched yarn thereon for a period of time between about 30 and seconds; applying an aqueous acid solution to the advancing helix of yarn on said second reel, said aqueous acid solution having a sulfuric acid concentration between about 1% and 5%, by weight; said acid solution treatment being performed at a temperature between about and C.; transferring said treated yarn discharged from said second reel, while still wet with said dilute aqueous acid solution, to a third thread-advancing, thread-storage reel; ap-

plying an aqueous oxidizing solution comprising sodium hypochlorite to the advancing helix on said third reel; the number of helical turns of thread on said third reel being sufllcient to store the advancing thread in the presence of said oxidizing solution for a period of time between about 30 and 60 seconds; said oxidizing solution having a pH between about 7 and 10 and an available chlorine content between about 0.005% and 0.05%; and thereafter removing said oxidizing solution from said treated yarn; said oxidizing treatment being performed without the intervention of a separate desulfurizing treatment between it and said aqueous acid treatment.

28. A process for the manufacture of viscose rayon yarn in accordance with claim 27 in which the viscose spinning solution is made from a cellulose containing, by weight, less than 0.5% lignin and in which the yarn in subjected to the treatment with the aqueous acid solution while 'it is in an incompletely regenerated state.

29. A process for the manufacture of viscose rayon yarn according to claim 25 in which the aqueous oxidizing solution comprises hyncchlorous acid.

MARCUS D. RODGERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Pellerin Feb. 16, 1915 2,309,072 Burkholder Jan. 19, 1943 2,845,822 Mothwurf Apr. 4, 1944 @ertificate of Correction Patent No. 2,521,748 September 12, 1950 MARCUS D. RODGERS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 10, for 65 read 65 0.; line 53, for the Words or dissolved read of dissotved; column 5, line 5, for thread advancing read thread-advancing; column 9, line 64, for oxdizing read oxidizing; column 12, line 20, before second strike out said; and that the said Letters Patent should be read as correctedabove, so that the same may conform to the record of the case in the Patent Oifice.

Signed and sealed this 19th day of December, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

1. A PROCESS FOR THE MANUFACTURE OF VISCOSE YARNS, STRIPS, FILMS AND THE LIKE WHICH COMPRISES EXTRUDING A VISCOSE SOLUTION INTO AN ACID COAGULATING BATH; WITHDRAWING THE RESULTING MATERIAL FROM SAID BATH; TREATING SAID MATERIAL AT A TEMPERATURE MAINTAINED BETWEEN ABOUT 65*C. AND 100*C. WITH AN AQUEOUS ACID SOLUTION; TREATING 